1. Field of the Invention
The present invention relates to a nonvolatile semiconductor device and particularly concerns a nonvolatile bistable memory device comprising a negative resistance device.
2. Description of the Prior Arts
By making use of an electrically bistable circuit device such as a flip-flop device or a negative resistance device, a memory device can be made. Recently, many memory devices are used in the field of information memory.
Most of the conventional memory devices have the shortcoming of instability such as change or maloperation of memorized contents in case of power failure, such as voltage change or voltage cut-off. For example, when the power supply is cut off and restored thereafter, it is not certain which of the bistable states the devices were in, and it is not assured that a state of memory before the power cut off is restored. Therefore, in such memory device, in the view point of reliable memorization of the information, we must understand that the memorized information has been erased upon the power failure.